1. Field of the Invention
The present invention is directed to a relatively compact wide angle zoom lens system and more particularly to a two group zoom lens system having a negative front group and a positive rear group wherein the zooming mode of operation can be achieved by varying the air space formed between the front and rear lens groups.
2. Brief Description of the Prior Art
Both professional and amateur photographers have been increasingly purchasing zoom lens systems as opposed to single fixed focal length lenses in the range of 28 to 300 mm. Modern zoom lens systems were introduced in the 1950's and have become increasingly popular in the 1970's.
A particular limitation in zoom lens systems is that they are not readily adaptable to a wide angle format particularly when it is desired to maintain a relatively lightweight compact lens system. The use of a two group zoom lens system will generally produce a tendency to create substantial changes in aberrations such as spherical aberration, coma and distortion during the zooming operation. Additionally, the total length of the system tends to be increased since the zoom system is of the retrofocus type.
Various forms of two lens group zoom lens systems have been suggested in the prior art such as disclosed in the German Offenlegungsschrift No. 2,557,547; Japanese Pat. Publication No. 40-8985; and Japanese Patent Applications laid open to public inspection No. 49-2548 and No. 51-83543.
The German Offenlegungsschrift is of some interest in that it discloses a zoom lens system having a positive front component. A two lens group zoom lens system of this type is suitable for a zooming mode of operation in the range of wide angle photography since it provides a power distribution of a retrofocus type. However, the spherical aberration related to the higher order of aberration coefficients tends to be insufficiently corrected when the zoom lens system is set at the longest focal length. Additionally, substantial variations of aberrations such as distortion and coma occur during the variation of the focal length.
Manufacturers are still seeking to provide a relative compact and economical wide angle two lens group zoom lens system with adequate optical correction.